It's a rather long time since I did these particular layups but, in general,
the manual is what I shall charitably call cavalier about being consistent
(and in worse ways than cm vs mm). Measure twice, cut once is not
sufficient because one must also verify the correctness of EVERY dimension
specified or risk cutting some critical part undersize. Not all the time,
mind you, but often enough that you MUST verify all critical cuts - do not
trust the book. In this particular instance it is easy enough to make you
own measurements, as you have already done. Trust your numbers.
The manual's inconsistencies also make it necessary to read ahead (sometimes
WAY ahead) in the book to see the consequences of today's work for some
future operation. For example, I am currently installing both the nose gear
assembly and the engine but had I finished the nose gear installation first
(per the manual), there would be no way to get my hands into the tunnel -
something necessary to run, for example, the fuel lines from the pumps to
the engine. Of course, with the big gaping opening for the Monowheel there
would be lots of access, I suppose, so this might just be a problem with the
Tri-Gear.
And....I too, am waiting for responses while the crew is at Sun 'n' Fun.
Best regards,
Rob Housman
A070
-----Original Message-----
Behalf Of Rowland & Wilma Carson
Subject: tailplane rear closeout dimensions
Having hacked off my first anti-servo tab, I'm about to tackle the
tailplane rear close-out.
The dimensions given in the manual for the principal pieces seemed
out of proportion to the actual shape of the tailplane, so I did some
measuring.
The rear face of the exposed foam measures about 650mm from the
trough at the tab-tip end to the face that forms the root rib. The
manual calls for 65cm x 10cm (I wish they'd stick consistently to mm,
I find that much easier for some reason) and also says that all
overlaps must be on the fore-and-aft surfaces, with none on the
trailing edge face.
So, to allow the desired 20-30mm overlap, the rear closeout piece
should be 710mm x 100m.
The root rib area does not seem to need the 80cm length called for,
and I would be happy with 770mm here (ie, 30mm shorter). (Yes, I
remembered the edges go right to the TE of the glass, and there's
enough for the LE flange too.)
Could it be that the dimensions given were perhaps for a previous
layup scheme where the overlaps were on the rear face? Then when they
discovered that made things a bit tight for hinging the tab, they
changed the words but forgot to change the sizes. The only evidence
against this deduction is that the tip rib is already pretty nearly
correctly dimensioned for no overlap onto the rear closeout.
Cross-checking the dimensions called out for the trim tab itself a
few pages later shows that I have made no gross errors in any of my
measurements or cutting lines.
I guess the factory are all at Sun'n'Fun and much too busy to watch
the forum at present, but has anyone else noticed this discrepancy,
or would anyone care to comment? Perhaps the volatile nature of BID
dimensions once bias-cut have let people get away with slightly wrong
sizes?
regards
Rowland
| PFA 16532 EAA 168386 Young Eagles Flight Leader 017623
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